Micro-electromechanical system device and method of forming the same

Abstract

The present disclosure relates to a micro-electromechanical system (MEMS) device and a method of forming the same. The MEMS device includes a substrate, a cavity, an interconnection structure and a proof mass. The substrate includes a first surface and a second surface opposite to the first surface. The cavity is disposed in the substrate, extending between the first surface and the second surface. The interconnection structure is disposed on the first surface of the substrate, over the cavity. The proof mass is disposed in the cavity, connected to the interconnection structure, the proof mass having a thickness which is smaller than a thickness of the substrate.

What is claimed is: 
     
         1 . A true wireless stereo earphone, comprising a micro-electromechanical structure, wherein the micro-electromechanical structure comprises:
 a micro-electromechanical substrate, comprising a first surface and a second surface opposite to the first surface, wherein the micro-electromechanical substrate comprises a first semiconductor layer, an insulating layer and a second semiconductor layer from bottom to top, and the insulating layer is in direct contact with both the first semiconductor layer and the second semiconductor layer to construct a silicon-on-insulator substrate;   a cavity disposed in the micro-electromechanical substrate, penetrating through the first semiconductor layer, the insulating layer and the second semiconductor layer;   an interconnection structure disposed on the first surface of the micro-electromechanical substrate, over the cavity, wherein the interconnection structure comprises a suspended region, one of the two opposite ends of the suspended region directly connects to the micro-electromechanical substrate and another one of the two opposite ends of the suspended region disconnect to the micro-electromechanical substrate; and   a proof mass disposed in the cavity and connected to the suspended region of the interconnection structure, close to and misaligned with the another one of the two opposite ends of the suspended region, the proof mass having a thickness which is ¼-⅛ of a thickness of the micro-electromechanical substrate.   
     
     
         2 . The true wireless stereo earphone accordingly to  claim 1 , wherein the substrate comprises a bulk silicon substrate and a material of the proof mass is the same as a material of the bulk silicon substrate. 
     
     
         3 . The true wireless stereo earphone according to  claim 1 , wherein a material of the proof mass is the same as a material of the second semiconductor layer. 
     
     
         4 . The true wireless stereo earphone according to  claim 3 , wherein the thickness of the proof mass is the same as a thickness of the second semiconductor layer that is disposed above the insulating layer of the silicon-on-insulator substrate. 
     
     
         5 . The true wireless stereo earphone according to  claim 3 , wherein a depth of the cavity is greater than the thickness of the proof mass. 
     
     
         6 . The true wireless stereo earphone according to  claim 1 , wherein the interconnection structure comprises a suspended structure disposed corresponding to the cavity and the proof mass. 
     
     
         7 . The true wireless stereo earphone according to  claim 1 , further comprising an oxide layer disposed between the interconnection structure and the second semiconductor layer, wherein a depth of the cavity is the same as the sum of thicknesses of the first semiconductor layer, the insulating layer, the second semiconductor layer and the oxide layer.